The present invention, in some embodiments thereof, relates to Additive Manufacturing (AM) of an object, and, more particularly, but not exclusively, to formulations, methods and systems for additive manufacturing of an object which exhibits desirable mechanical properties, for example, a desirable Heat Deflection Temperature (HDT) without compromising other properties.
Additive manufacturing is generally a process in which a three-dimensional (3D) object is manufactured utilizing a computer model of the objects. Such a process is used in various fields, such as design related fields for purposes of visualization, demonstration and mechanical prototyping, as well as for rapid manufacturing (RM).
The basic operation of any AM system consists of slicing a three-dimensional computer model into thin cross sections, translating the result into two-dimensional position data and feeding the data to control equipment which manufacture a three-dimensional structure in a layerwise manner.
Various AM technologies exist, amongst which are stereolithography, digital light processing (DLP), and three dimensional (3D) printing, 3D inkjet printing in particular. Such techniques are generally performed by layer by layer deposition and solidification of one or building materials, typically photopolymerizable (photocurable) materials.
Stereolithography, for example, is an additive manufacturing process which employs a liquid UV-curable building material and a UV laser. In such a process, for each dispensed layer of the building material, the laser beam traces a cross-section of the part pattern on the surface of the dispensed liquid building material. Exposure to the UV laser light cures and solidifies the pattern traced on the building material and joins it to the layer below. After being built, the formed parts are immersed in a chemical bath in order to be cleaned of excess building material and are subsequently cured in an ultraviolet oven.
In three-dimensional inkjet printing processes, for example, a building material is dispensed from a dispensing head having a set of nozzles to deposit layers on a supporting structure. Depending on the building material, the layers may then be cured or solidified using a suitable device.
Various three-dimensional inkjet printing techniques exist and are disclosed in, e.g., U.S. Pat. Nos. 6,259,962, 6,569,373, 6,658,314, 6,850,334, 7,183,335, 7,209,797, 7,225,045, 7,300,619, 7,479,510, 7,500,846, 7,962,237, 9,031,680 and U.S. Patent Application having Publication No. 2015/0210010, all of the same Assignee.
A printing system utilized in additive manufacturing may include a receiving medium and one or more printing heads. The receiving medium can be, for example, a fabrication tray that may include a horizontal surface to carry the material dispensed from the printing head. The printing head may be, for example, an ink jet head having a plurality of dispensing nozzles arranged in an array of one or more rows along the longitudinal axis of the printing head. The printing head may be located such that its longitudinal axis is substantially parallel to the indexing direction. The printing system may further include a controller, such as a microprocessor to control the printing process, including the movement of the printing head according to a pre-defined scanning plan (e.g., a CAD configuration converted to a Stereo Lithography (STL) format and programmed into the controller). The printing head may include a plurality of jetting nozzles. The jetting nozzles dispense material onto the receiving medium to create the layers representing cross sections of a 3D object.
In addition to the printing head, there may be a source of curing energy, for curing the dispensed building material. The curing energy is typically radiation, for example, UV radiation.
Additionally, the printing system may include a leveling device for leveling and/or establishing the height of each layer after deposition and at least partial solidification, prior to the deposition of a subsequent layer.
The building materials may include modeling materials and support materials, which form the object and the temporary support constructions supporting the object as it is being built, respectively.
The modeling material (which may include one or more material) is deposited to produce the desired object/s and the support material (which may include one or more materials) is used, with or without modeling material elements, to provide support structures for specific areas of the object during building and assure adequate vertical placement of subsequent object layers, e.g., in cases where objects include overhanging features or shapes such as curved geometries, negative angles, voids, and so on.
Both the modeling and support materials are preferably liquid at the working temperature at which they are dispensed, and subsequently hardened, typically upon exposure to curing energy (e.g., UV curing), to form the required layer shape. After printing completion, support structures are removed to reveal the final shape of the fabricated 3D object.
Several additive manufacturing processes allow additive formation of objects using more than one modeling material. For example, U.S. Patent Application having Publication No. 2010/0191360 of the present Assignee, discloses a system which comprises a solid freeform fabrication apparatus having a plurality of dispensing heads, a building material supply apparatus configured to supply a plurality of building materials to the fabrication apparatus, and a control unit configured for controlling the fabrication and supply apparatus. The system has several operation modes. In one mode, all dispensing heads operate during a single building scan cycle of the fabrication apparatus. In another mode, one or more of the dispensing heads is not operative during a single building scan cycle or part thereof.
In a 3D inkjet printing process such as Polyjet™ (Stratasys Ltd., Israel), the building material is selectively jetted from one or more printing heads and deposited onto a fabrication tray in consecutive layers according to a pre-determined configuration as defined by a software file.
When a cured rigid modeling material forms the final object, the cured material should preferably exhibit heat deflection temperature (HDT) which is higher than room temperature, in order to assure its usability. Typically, the cured modeling material should exhibit HDT of at least 35° C. For an object to be stable in variable conditions, a higher HDT is desirable.
U.S. Patent Application having Publication No. 2013/0040091, by the present assignee, discloses methods and systems for solid freeform fabrication of shelled objects, constructed from a plurality of layers and a layered core constituting core regions and a layered shell constituting envelope regions.